In a thermal power plant or the like in which a large amount of a fossil fuel is used, exhaust gas generated due to the combustion of a fossil fuel in a boiler, coal gasified gas (gasified gas) obtained by gasifying coal, and natural gas contain acidic gas components (for example, H2S, CO2 and the like). Gas containing the above-described acidic components is brought into gas-liquid contact with an amine-based acidic gas-absorbing solution in an absorption tower so that acidic gas is absorbed in the acidic gas-absorbing solution, whereby the acidic gas in the gas is removed and recovered.
For example, a method is used in which an acidic gas-absorbing solution absorbs and removes acidic gas in gas such as exhaust gas and gasified gas in the absorption tower, then, the acidic gas absorbed in the acid gas-absorbing solution is released in a regeneration tower, the regenerated acidic gas-absorbing solution is resupplied to the absorption tower and reused, and the acidic gas-absorbing solution is circulated into a circulation system between the absorption tower and the regeneration tower, and used (for example, refer to PTL 1 and 2).
In a step of recovering the acidic gas component (for example, CO2, SO2 and the like) from exhaust gas exhausted from a boiler and a step of removing acidic gas components (H2S, CO2) in natural gas or coal gasified gas exhausted from a gasification furnace or the like, the amine-based acidic gas-absorbing solution being used generates a degradant called heat stable amine salt (HSAS) due to the degradation reaction of treatment gas components or decomposition of the acidic gas-absorbing solution.
Since a degradant generated due to the acidic gas-absorbing solution is highly corrosive, it is necessary to manage the degradant below the management concentration. As a method for managing the concentration of the degradant contained in the acidic gas-absorbing solution, for example, a method in which, when the concentration of a degradant in an acidic gas-absorbing solution circulating in the circulation system exceeds a prescribed value, the full amount of a degradant-absorbing solution in the circulation system is extracted and exchanged with a new absorbing solution, a method in which, while continuously carrying out an operation in the circulation system, some of an acidic gas-absorbing solution extracted from the circulation system is supplied to a reclaimer so as to remove a degradant in the acidic gas-absorbing solution, and the acidic gas-absorbing solution is returned to the circulation system, and the like are carried out.
In a case in which the reclaimer is used, when the concentration of the degradant in the acidic gas-absorbing solution circulating in the circulation system exceeds a prescribed value, some of the acidic gas-absorbing solution circulating in the circulation system is extracted and supplied to the reclaimer, the degradant in the acidic gas-absorbing solution is removed in the reclaimer, and the acidic gas-absorbing solution is returned to the circulating system. As described above, in the related art, the concentration of the degradant in the acidic gas-absorbing solution circulating in the circulation system is directly measured, and the reclaimer is repeatedly operated depending on the concentration.